Dishwasher control



Dec. o LONG DISHWASHER CONTROL Filed Feb. 28, 1966 W4? W ATTORN E INVENTOR Olon L. Long' United States Patent Oflice 3,415 ,2 6 l Patented Dec. 10, 1968 3,415,261 DISHWASHER CONTROL Olan L. Long, Lafayette, Ind., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 28, 1966, Ser. No. 530,561

5 Claims. (Cl. 137-2) ABSTRACT OF THE DISCLOSURE A water fill control arrangement for a dishwasher in which the pump, which draws water from the dishwasher sump and forces it through separate passage means back into the dishwasher, has an inlet arrangement which results in the pump drawing partly air and cavitating until the sump water level reaches the proper fill height, at which time means responsive to pump pressure sense the full pump pressure and terminate the water fill.

This invention relates generally to dishwashers, and particularly to an arrangement for controlling the admission of water to the dishwasher.

One common way of controlling the supply of water to a dishwasher is to open the supply valve to admit water for a predetermined time at the beginning of each wash and rinse cycle with the time control being effected by a timer. With the so-called time fill thus obtained the amount of water admitted to the dishwasher will be dependent in part upon the supply water pressure and will not necessarily bear any relation to the proper amount of water for the dish load to be washed.

In a typical dishwasher of the type which includes a pump forcing water to a distributing means which flings the water about the interior of the washing chamber, the proper amount of water for a given dish load may be considered to comprise two general parts. One quantity of water is the pool at the bottom of the washing chamber which the pump draws upon. The remaining water includes the water which is in transit to the distributing means, plus the water being flung about the chamber, plus the water which is draining back to the pool from the dishes and the interior structure at any given time. It will be appreciated that with a large dish load more water will be retained on the surfaces of the dishes at any given time during the washing cycle than with a small load. Thus a larger total quantity of water is required in the dishwasher to provide an adequate pool at the bottom of the chamber which the pump draws upon. It will also be appreciated that a pool which provides more water than is necessary to supply the pump is wasteful. However, as a practical matter, to insure that suflicient water is present for the largest load of dishes likely to be washed, the time setting of conventional dishwashers is made sufiiciently long that more Water than normally is necessary is admitted to the dishwasher.

An object of this invention is the elimination of a time fill, and the provision of a fill arrangement which corresponds more closely with the quantity of water required for the particular load.

In accordance with the invention, the control of supply water to the dishwasher is made responsive to the pressure developed by the pump furnishing the water to the distribution means. Inlet means for the pump is provided which restricts the admission of water to the pump until a chamber water level corresponding to the proper level for satisfactory pump operation is reached. The restriction may conveniently be accomplished by providing a separate passage means which serves as part of the inlet means of the pump, and which receives water at a substantial rate only after the level of water in the chamber reaches a given level. Until the water reaches this level, the pump draws both water and air and accordingly is subject to cavitation and develops a substantially lower pressure than when it is drawing only water into its inlet. When only water is being drawn into the inlet the increased pressure developed by the pump is used to stop the admission of water to the dishwasher.

The invention will be described in connection with the accompanying drawing illustrating one embodiment by way of example, and wherein:

FIGURE 1 is a partly-schematic, partly-broken view of an arrangement incorporating the invention; and

FIG. 2 is a horizontal section corresponding to one taken along the line IIII of FIG. 1.

The invention may be incorporated in various pumping arrangements for dishwashers. However, I will describe it in connection with the general arrangement disclosed and claimed in U.S. Patent application S.N. 331,046, now U.S. Patent 3,210,009.

FIGURE 1 view is mainly directed to structure found in the lower part of a dishwasher including a water filter arrangement, a pump arrangement for both recirculating the water in the chamber and for ultimately draining the Water from the chamber, distribution means in the form of a rotatable arm which flings the water received from the recirculating pump about the washing chamber, and a schematic representation of the pressure responsive means and electrical circuits associated with this part of the device.

The washing chamber is conventional and includes one pair of sidewalls 10 and another pair 12. A fragmentary portion of one of the sidewalls 12 facing the viewer includes an opening 14 through which water discharged from supply pipe 16 enters the chamber. The water flows into a sump 18 at the bottom of the chamber where it pools or accumulates to the extent it is not drawn therefrom by the recirculating ump 20.

The sump 18 is mostly covered by a filtering screen 22 which also encircles the mouth of a depending central funnel 24 which in the embodiment shown has perforated walls except in one segment. The funnel conveys some water and food debris down to the eye of a drain pump 26 which is in communication with a drain passage 28 having an outlet valve 30. The recirculation pump 20 is also in communication with the drain pump through a bypass passage 32. Details of the structural relationship of these parts to each other and their function is explained in the noted application.

For present purposes it is noted that when the motor shaft 34 is rotated, the pump impellers of both the recirculating pump 20 and drain pump 26 rotate together and recirculation of Water takes place within the washing chamber until the drain valve 30 is opened to exhaust the Water from the chamber. The recirculation pumping action is mainly effected by the recirculation pump 20 which forces water drawn from the sump about its volute 36 and up the standpipe 38 to the distribution arm 40 through which water is forced and flung out into the washing chamber. Water is admitted from the sump 18' into the recirculating pump 20 through the circular inlet 42 surrounding the funnel 24 and through the eye of the funnel. A number of upstanding fins 44 formed as part of the top plate 48 of the pump assembly may be provided to reduce swirling of water flowing into the inlet 42.

In accordance with the invention, the inlet to the recirculating pump is intentionally partially starved until the water level in the sump reaches a predetermined level such as that indicated by the level 46 in FIG. 1. One convenient way of accomplishing this is a separate the inlet of the pump into several parts, one part of which admits water from .a level such as the floor of the sump, and another part which admits water only when the water level rises to the indicated line 46. This may be conveniently accomplished in the arrangement shown by providing a wall (FIGS. 1 and 2) between two adjacent fins 44 to form an upwardly-open passage with the solid portion segment of the funnel 24. When the level of 'water is below the indicated level 46 the pump 20 draws partly water and partly air so that cavitation occurs and it fails to develop its full pressure. However, when the water level has risen above the indicated level 46 the pump draws a full supply of water and develops a substantially greater pressure.

To utilize the differential in pressure developed by the pump under its different operating conditions, pressure responsive means are provided to sense the pressure in the volute, or at any other convenient location, and control a supply valve 50 in the water supply line.

The pressure responsive means schematically shown herein as an example includes a diaphragm 52 in a chamber in communication with the pump volute, the movement of the diaphragm controlling an electrical switch 54 which in turn controls energization of the solenoid 56 for the valve 50. The switch 54 is in series with a switch 58 controlled by a timer 60. The function of the timer control switch 58 is to permit the energization of the solenoid 56 to open the valve 50 and admit the water during the appropriate portions of the dishwasher cycle, and to prevent the energization and the supply of water during all of the other periods when it is not appropriate to add water to the dishwasher For example, the timer may be arranged so that switch 58 is closed during the early part of each wash and rinse cycle, and is opened during the remainder of the total dishwasher cycle. However, the switch 58 should remain closed during these early periods of the wash and rinse operations to provide ample time for the actual control of the supply water to be effected by the pressure responsive means. This poses no particular problem, since the wash and rinse cycles are usually of relatively extended length compared to the time it normally takes to admit sufficient water.

It is to be understood that the means provided to partially starve the inlet of the recirculation pump 20 may take various forms, the specific arrangement shown being simply one example.

In summary as to the operation of the dishwasher with the arrangement according to the invention, when the dishwasher is started the switch 58 is closed and the relatively low pressure developed by the recirculation pump 20 permits switch 54 to remain closed and thereby energize the solenoid 56. Thus valve 50 is opened to admit water to the washing chamber through the pipe 16. The water admitted flows into the sump and int-o the recirculation pump inlet 42 through those parts of the inlet which are substantially at the level of the sump floor. This water, and the air sucked in through the starved part of the inlet is pumped up through the standpipe 38 for distribution out of the rotating arm 40. As additional water is introduced to the chamber, the level of water in the sump 18 rises until it overflows the edge of the wall 48. When the inlet of the recirculation pump is substantially flooded the pump operates without substantial cavitation. The increased pressure developed by the pump is sensed by the pressure responsive means so that the valve 50 is closed in the fashion explained before. After the washing cycle has been completed, the drain valve 30 is opened so that the drain pump exhausts the water from the chamber. By this time of course the switch 58 controlled by the timer has opened so that the reduced pressure sensed by the pressure responsive means and which causes the switch 54 to close does not complete the circuit to the solenoid 56. For rinse operations or any other operations which require water, the switch 58 is again closed permitting the introduction of water for such portions of the cycle. By the time the last operation requiring water has been completed, and before the drying cycle begins, the switch 58 controlled by the timer has again opened so that the pressure condition in the recirculation pump system does not cause the supply valve to again open.

The advantages of the arrangement may now be readily appreciated. First, the water fill is not controlled by a set time period, but on the contrary is controlled by the water level in the sump. Accordingly the variations in water supply pressure frequently encountered are of no effect as to the admission of the proper quantity of water. The proper quantity of water is admitted irrespective of the dish load. Thus with a heavy load upon which more water droplets are retained in their passage back to the sump, more water is admitted than for a small load. In either case the total quantity of water admitted to the dishwasher is still only that quantity required for proper recirculaion pump operation. The arrangement also inherently provides flood protection.

Still another advantage is that in cases of the type of pump cavitation caused by suds from the dishwasher detergent, additional water will be taken into the dishwasher until a normal pressure head can be developed by the pump.

Having described my invention I claim:

1. Dishwashing apparatus comprising: a washing chamber having a sump at the bottom thereof; a pump located out of said chamber for drawing water down out of said sump forcing it back up into said chamber through passage means separate from said chamber; said pump including inlet means divided into one part in communication with said sump at a lower level, and another part in communication with said sump at an upper level so that said pump develops a reduced pressure until said pump inlet means draws water through both of said parts; valve means for controlling the admission of water to said chamber; and means responsive to the pressure developed by said pump in said passage means for controlling said valve means.

2. Dishwasher apparatus according to claim 1 wherein: means are provided to disable control of said valve means by said pressure responsive means during selected portions of a dishwashing cycle.

3. Dishwashing apparatus as claimed in claim 1 where in: said pump comprises a centrifugal pump having a volute, forming a part of said passage means, and said pressure responsive means is connected to respond to the pressure developed by said pump in said volute.

4. Dishwasher apparatus according to claim 2: said other part of said pump inlet means includes means forming an open-ended passage in communication with said sump only at its upper end.

5. The method of controlling the admission of water to a dishwasher chamber having a pump connected to a sump of said chamber for drawing said water from said sump and forcing said water through passage means separate from said chamber back into said chamber at a higher level, said method comprising: admitting water to said chamber; restricting the rate of supply of said water to said pump to cause said pump to cavitate until a predetermined level of said water in said dishwasher chamber is reached; directing said water through said passage means; and terminating the admission of water to said dishwasher chamber in response to the increased pressure in said passage means developed by said pump operating without substantial cavitation after said level is reached.

References Cited UNITED STATES PATENTS 7/1951 Clark 134-57 8/1963 La Flame l03-3 X 

